Gas turbine engines include compressor, combustor and turbine sections that operate cooperatively to rotate a shaft. In an aircraft engine, the shaft rotation operates in conjunction with other engine systems, such as a fan, to generate thrust. Each of the turbine engine sections is encapsulated by a cylindrical, or approximately cylindrical, case structure that provides structural support for the components within the case, as well as protecting the components.
One type of case commonly used for gas turbine engines is a split case. A split case includes two or more partial case components that are combined to form a full case. Each partial case component includes a pair of axially aligned flanges (referred to as split flanges). The split flanges of each partial case component are connected to split flanges of at least one other partial case component to form a complete split case. In some examples, a complete split case includes two partial case components. Alternate designs can include three or more case components. The complete split case includes a circumferential flange on each axial end. The circumferential flanges connect the case to an adjacent engine structure, such as a fan section or another case section.
Due to the nature of split cases, split cases frequently have a condition in which assembly fits combined with thermal growth, cause separation in the split flange at an associated circumferential flange. The separation causes deflection in adjacent hardware, such as an adjacent gas turbine engine structure. The deflection, in turn, causes a corresponding high stress region in the adjacent gas turbine engine structure.